Transfer type grounding line selection device suitable for three sections of buses and working method of transfer type grounding line selection device
By designing a transfer-type grounding line selection device suitable for three-stage busbars, using components such as separate grounding switches, zero-sequence current transformers and voltage transformers, the grounding line and transfer busbar are accurately selected after the inverted busbar is run, solving the problem of inaccurate grounding fault handling in the existing technology and improving the power supply reliability of the power grid.
Patent Information
- Application Number
- CN202510226498.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-27
- Publication Date
- 2025-06-20
AI Technical Summary
In the power grid structure of three-stage busbars, it is difficult for the prior art to accurately select the grounding line and transfer busbar after the inverted busbar is running, resulting in inaccurate grounding fault handling and prone to short-circuit blasting accidents in electrical equipment.
A transfer-type grounding wire selection device suitable for three-stage busbars is designed, including a phase-divided grounding switch, a high-voltage cable, a zero-sequence current transformer, a voltage transformer, a current input module and a voltage input module. Through the cooperation of these components, real-time monitoring and comparison of grounding current and voltage can be achieved, and the grounding circuit and transfer busbar are accurately judged.
In complex operation mode, the device improves the accuracy of grounding wire selection, avoids the occurrence of wrong busbars and lines when grounding, reduces the number of back-off operations, suppresses arc grounding overvoltage, reduces the probability of phase-to-phase short circuit accidents, and improves the reliability of power supply.
Smart Images
Figure CN120177931A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of distribution network grounding, and more particularly, to a transfer type grounding line selection device applicable to three-section busbars and its working method. Background Art
[0002] The power grid structure of large steel enterprises is very complex, and single-phase grounding faults of the system often occur.
[0003] The traditional method for dealing with single-phase grounding faults of the system is to determine the grounding line according to the result of the grounding line selection device or by means of switching the busbars or cycling out the distribution lines. Since the accuracy rate of the grounding line selection device is very low, generally, according to the characteristics of the operation mode, the grounding line is selected by relying on switching operations and specific sequential power outages. During the grounding selection operation (such as closing and opening the bus coupler and other circuit breakers) and in the case of intermittent arc grounding accidents, short-circuit blasting accidents of electrical equipment often occur. At the same time, since the operation mode of the substation is a three-busbar three-section operation mode, and any two of them can be operated in parallel, there are certain difficulties in ensuring that the line selection device can still reliably select the grounding of the local line after the busbar is switched and the grounding transfer busbar is reliable and correct. Summary of the Invention
[0004] In view of the above-mentioned technical problems existing in the current grounding line selection for three-section busbars, a transfer type grounding line selection device applicable to three-section busbars and its working method are provided. The present invention mainly provides a transfer type grounding line selection device. When this device is applied to a substation with a three-busbar three-section operation mode, it ensures that the line selection device can reliably select the grounding of the local line after the busbar is switched and the grounding transfer busbar is reliable and correct.
[0005] The technical means adopted by the present invention are as follows:
[0006] A transfer type grounding line selection device applicable to three-section busbars, comprising a phase-separated grounding switch, a high-voltage cable, a zero-sequence current transformer, a voltage transformer, a current input module, and a voltage input module;
[0007] Each section of the three-section busbars is respectively connected to one end of a three-core high-voltage cable through a high-voltage circuit breaker, and the other ends of the three cores of the high-voltage cable are connected to a three-phase phase-separated grounding switch;
[0008] The three-section busbars are respectively connected to a number of lines, and zero-sequence current transformers are arranged below the cable heads of the lines; the capacitive current of each line is connected to the current input module through a communication cable connected to the secondary outlet of the zero-sequence current transformer;
[0009] The three-section busbars are respectively connected to their own voltage transformers, and the voltage transformers are connected to the voltage input module through secondary cables.
[0010] Further, the bus is connected to the high-voltage cable through a first high-voltage circuit breaker, and the bus is connected to the voltage transformer through a second high-voltage circuit breaker.
[0011] Further, the current-carrying capacity of the high-voltage cable is greater than the maximum capacitive current of the system.
[0012] The present invention also provides a working method for a transfer-type grounding line selection device applicable to three-section buses, which is implemented based on any one of the transfer-type grounding line selection devices applicable to three-section buses, and includes the following steps:
[0013] Assume that the grounded phase of the system is phase X. When the system is grounded in phase X, close the fast grounding switch directly connected to the bus, turn the grounded phase of the bus into a solid ground, and transfer all the grounding capacitive currents to the grounding electrode behind the grounding switch of its phase X.
[0014] The line selection device compares the magnitudes and directions of the capacitive currents of all lines before and after the grounding switch operates, that is, before and after the capacitive current is transferred: before the transfer, the grounding current of all normal lines is from the bus to the line, the zero-sequence current is the capacitive current of this line and is less than the rated value, the grounding current of the grounded line is from the line to the bus, and the zero-sequence current is the sum of the capacitive currents of other lines. When the grounding switch of phase X of the line selection device operates, because the reactance from the fast switch to the grounding electrode is the smallest, the grounding currents of all lines, including the grounded line, flow to the fast grounding switch of phase X. The magnitude and direction of the capacitive current of the normal line remain unchanged before and after the transfer. The magnitude of the zero-sequence current of the grounded line changes from the sum of the capacitive currents of all lines to the capacitive current of this line, and the current direction changes from the line to the bus to the bus to the line. Based on this, it is determined that the line with the largest change amount and the changed direction is the grounded line.
[0015] Further, the speed of transferring all the grounding capacitive currents to the grounding electrode behind the grounding switch of its phase X is faster than the operating speed of the arc suppression coil.
[0016] Further, the sum of the capacitive currents of all lines before the transfer is greater than 30 A, and the range of the capacitive current of this line is 1 - 5 A.
[0017] Further, it also includes:
[0018] Set the priorities of the three-section buses, collect the auxiliary contacts of the bus-tie switch, and only the grounding switch of the bus with a higher priority operates after the bus-tie switch is closed.
[0019] Compared with the prior art, the present invention has the following advantages:
[0020] The present invention meets the requirements for the accuracy of grounding line selection under complex operating modes. At the same time, it avoids the situation where only the transfer switch corresponding to the phase of the bus where the grounded line is located operates when there is a ground fault after the load on the double busbars is transferred during the busbar transfer operation, thus avoiding the occurrence of misselecting the busbar and the line. It minimizes the number of switching operations to the greatest extent, instantaneously transfers capacitive current, suppresses arc grounding overvoltage, reduces the probability of phase-to-phase short-circuit accidents caused by electric arcs, reduces the risk of personal electric shock, and improves the power supply reliability. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.
[0022] Figure 1 It is the connection schematic diagram of the grounding line selection device of the present invention.
[0023] Figure 2 It is the schematic diagram of the grounding busbar and grounding phase selection of the present invention.
[0024] Figure 3 It is the schematic diagram of the grounding line selection of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0025] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The following will describe the present invention in detail with reference to the drawings and in combination with the embodiments.
[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. The description of at least one exemplary embodiment below is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.
[0027] It should be noted that the terms used here are only for describing the specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used here, unless otherwise clearly specified in the context, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or their combinations.
[0028] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn according to the actual proportional relationship. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific values should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: similar reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.
[0029] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Without additional statements, the above terms have no special meaning and thus cannot be construed as a limitation on the protection scope of the present invention.
[0030] As Figure 1 shown, the present invention provides a transfer type grounding line selection device applicable to three-section busbars. A transfer type grounding line selection device applicable to three-section busbars includes a phase-separated grounding switch, a high-voltage cable, a zero-sequence current transformer, a voltage transformer, a current input module, and a voltage input module;
[0031] Each section of the three-section busbars is respectively connected to one end of a three-core high-voltage cable through a high-voltage circuit breaker, and the other ends of the three cores of the high-voltage cable are connected to a three-phase phase-separated grounding switch;
[0032] The three-section busbars are respectively connected to a number of lines, and zero-sequence current transformers are arranged below the cable heads of the lines; the capacitive current of each line is connected to the current input module through a communication cable connected to the secondary outlet of the zero-sequence current transformer;
[0033] The three-section busbars are respectively connected to their own voltage transformers, and the voltage transformers are connected to the voltage input module through secondary cables. The busbar is connected to the high-voltage cable through a first high-voltage circuit breaker. The busbar is connected to the voltage transformer through a second high-voltage circuit breaker.
[0034] By connecting a three-core flame-retardant cross-linked polyethylene high-voltage cable (with a current-carrying capacity greater than the maximum capacitive current of the system) to the outlet of a 10 kV high-voltage circuit breaker connected to the busbar, and directly accessing the inlet of the single-phase grounding switch circuit breaker, with the three-phase cables respectively connected to the three single-phase circuit breakers, the purpose of transferring the grounding capacitive current of the corresponding phase busbar after the single-phase circuit breaker operates can be achieved; a zero-sequence current transformer is newly installed below each line cable head, and the capacitive current (Ic) of the line is connected to the same grounding line selection device through a four-core 2.5 mm 2 communication cable, realizing real-time monitoring of the magnitude and direction of the capacitive current of each line; each section of the busbar has its own voltage transformer, and the voltage transformer is directly connected by the copper busbar inside the 10 kV high-voltage circuit breaker to monitor the voltage change of this section of the busbar. Finally, the voltage transformer also uses a four-core 2.5 mm 2 communication cable to access the grounding line selection device. Under the grounding state, the device comprehensively and real-time judges the changes in current and voltage, and finally issues an instruction to close the grounding switch of a certain phase of a certain section of the busbar.
[0035] Affected by the actual on-site operation requirements, the operation modes of some substations are relatively complex. For example, there is an operation mode in which three sections of busbars can be paralleled with each other. The operation mode of the three-section busbar is very complex. When there is a main transformer overhaul or on-site load transfer, the three bus coupler switches are sometimes in the closed state. Therefore, the outgoing lines may operate on bus I, or on bus II, or on bus III. Because the main judgment basis of the grounding line selection device is the zero-sequence current of each outgoing open circuit, if the zero-sequence current signals of each outgoing are respectively connected to the grounding line selection devices of the three sections of the busbar, with the change of the operation mode, a three-way switching device needs to be installed on the device, and the position of the manual switching clip needs to be adjusted according to the operation mode, which is very frequent and prone to errors. Once an operation error occurs, under the grounding state, if it is actually the grounding of line 1 on bus I, but the selection clip is selected on bus II, it is easy to cause the misoperation of the line selection device on bus II. Since the voltage on bus II has not changed, it will cause the misjudgment of the line selection system on bus II and the failure of line selection.
[0036] The main innovation point of this patent lies in the acquisition method of the zero-sequence current of each outgoing device: all the zero-sequence current signals are uniformly connected to a single grounding line selection device at the same time. Each of the three sections of the busbar uses an independent voltage acquisition device and three-phase grounding switches. Only when the open-circuit voltage is collected by the PT of this section, the grounding switch of this section will operate. In this way, it is judged which section of the busbar and which phase is grounded through the voltage signal, and it is judged which outgoing is grounded through the only line selection device. Finally, all the grounding information is reported in the background - ×× busbar ×× outgoing × phase grounding. It avoids the inconvenience and errors caused by the frequent operation of the zero-sequence current switching clips of each outgoing switch after the mode change.
[0037] Such as Figure 2 and Figure 3As shown in the figure, the present invention also provides a working method for a transfer-type grounding line selection device applicable to three-section busbars, including the following steps:
[0038] Suppose the grounded phase of the system is phase A. When the system is grounded at phase A, close the fast grounding switch directly connected to the busbar, convert the grounded phase A of the busbar into a solid ground, and quickly transfer all grounding capacitive currents (faster than the action speed of the arc suppression coil) to the grounding electrode behind the phase A grounding switch of it. The line selection device compares the magnitudes and directions of the capacitive currents of all lines before and after the action of the grounding switch, that is, before and after the transfer of the capacitive current: Because the grounding currents of all normal lines before the transfer are from the busbar to the line, and the zero-sequence current is the capacitive current of this line (relatively small), only the grounding current of the grounded line is from the line to the busbar, and the zero-sequence current is the sum of the capacitive currents of other lines (relatively large). After the phase A switch of the grounded phase of the line selection device acts, because the reactance from the fast switch to the grounding electrode is the smallest, the grounding currents of all lines including the grounded line flow to the phase A fast grounding switch. The magnitude and direction of the capacitive current of the normal line remain unchanged before and after the transfer, while the magnitude of the zero-sequence current of the grounded line changes from the sum of the capacitive currents of all lines (generally > 30A) to the capacitive current of this line (generally 1 - 5A), and the current direction changes from the line to the busbar to the busbar to the line. Therefore, it can be determined that the line with the largest change amount and the changed direction is the grounded line.
[0039] Through this configuration method, each section of the busbar only collects the voltage signal of this section, and the total line selection device calculates the magnitudes and directions of all distributed currents. At the same time, set priorities for the first, second, and third sections of the busbars, collect the auxiliary contacts of the bus-coupling switch. After the bus-coupling switch is closed, only the grounding switch of the busbar with a higher priority acts, avoiding the simultaneous action of two sets of line selection devices caused by system grounding when the busbars are in parallel. In this way, it can ensure that the accuracy rate of grounding busbar selection and grounding switch action is 100%. At the same time, based on the change situation of the currents of each line collected by the total line selection device, the accuracy rate of judging the grounded circuit is 100%, and it is not affected by the operating mode of each line. Each distribution can freely transfer the busbar for operation. This greatly improves the flexibility and accuracy of the use of the line selection device.
[0040] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: They can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A transfer type grounding line selection device suitable for three-section busbars, characterized in that: It includes a phase-splitting grounding switch, a high-voltage cable, a zero-sequence current transformer, a voltage transformer, a current input module and a voltage input module; Each of the three busbar sections is connected to one end of a three-core high-voltage cable through a high-voltage circuit breaker, and the other end of the three cores of the high-voltage cable is connected to a three-phase split-phase grounding switch; The three sections of busbars are respectively connected to a number of lines, and a zero-sequence current transformer is arranged below the cable head of the line; the capacitive current of each line is connected to the current input module through a communication cable connected to the secondary outlet of the zero-sequence current transformer; The three busbar sections are respectively connected to respective voltage transformers, and the voltage transformers are connected to a voltage input module via secondary cables.
2. The transfer type grounding line selection device applicable to three-section busbars according to claim 1 is characterized in that: The busbar is connected to the high-voltage cable through a first high-voltage circuit breaker, and the busbar is connected to the voltage transformer through a second high-voltage circuit breaker.
3. The transfer type grounding line selection device applicable to three-section busbars according to claim 1 is characterized in that: The current carrying capacity of the high voltage cable is greater than the maximum capacitive current of the system.
4. A working method of a transfer type grounding line selection device applicable to three-segment busbars, which is implemented based on the transfer type grounding line selection device applicable to three-segment busbars according to any one of claims 1 to 3, characterized in that: The steps include: Assume that the grounding phase of the system is phase X. When phase X of the system is grounded, close the fast grounding switch directly connected to the busbar, turn the grounding phase of the busbar into dead grounding, and transfer all grounding capacitance currents to the grounding electrode behind the phase X grounding switch. The line selection device compares the capacitive current magnitude and direction of all lines before and after the grounding switch is actuated, i.e., the capacitive current is transferred: before the transfer, the grounding current of all normal lines is the busbar pointing to the line, the zero-sequence current is the capacitive current of the line less than the rated value, the grounding current of the grounded line is the line pointing to the bus, and the zero-sequence current is the sum of the capacitive currents of other lines. When the grounding phase X-phase switch of the line selection device is actuated, because the reactance from the fast switch to the grounding electrode is the smallest, the grounding current of all lines including the grounding line flows to the X-phase fast grounding switch. The capacitive current magnitude and direction of the normal line remain unchanged before and after the transfer, the zero-sequence current magnitude of the grounding line changes from the sum of the capacitive currents of all the original lines to the capacitive current of the line, and the current direction changes from the line pointing to the busbar to the busbar pointing to the line, so as to determine that the line with the largest change and the changed direction is the grounding line.
5. The working method of the transfer type grounding line selection device applicable to three-segment busbars according to claim 4 is characterized in that: The speed of transferring all grounding capacitance current to the grounding electrode behind its X-phase grounding switch is faster than the arc suppression coil action speed.
6. The working method of the transfer type grounding line selection device applicable to three-segment busbars according to claim 4 is characterized in that: The sum of the capacitive currents of all lines before the transfer is greater than 30A, and the capacitive current of this line ranges from 1 to 5A.
7. The working method of the transfer type grounding line selection device applicable to three-section busbars according to claim 4 is characterized in that: Also includes: Set the priority of the three-section busbars and collect the auxiliary contacts of the bus tie switch. After the bus tie switch is closed, only the bus grounding switch with a higher priority will operate.